Agricultural chemicals are most preferably applied in the form of aqueous emulsions, solutions or suspensions. Occasionally, they may be applied in powder form where the active ingredient is absorbed onto or mixed with a finely divided inert carrier material, such as china clay or the like. However, such powder composition are subject to wind drift and consequently liquid formulations are preferred.
One problem with liquid formulations is that chemicals having agricultural activity often exhibit extremely poor solubility in water. Consequently, such chemicals are typically dissolved either in organic solvents or utilized in the form of emulsions or suspensions. The use of organic solvents presents particular disadvantages. For example, such solvents may exhibit toxicity or side effects which may be adverse to the effect of the agricultural chemical itself or to the fruit or vegetable produced in the particular agricultural use. This toxicity may also present difficulty with respect to handling and application procedures. Moreover, many organic solvents which have been used in the past, even those exhibiting relatively low toxicities, are not biodegradable and thus remain as a pollutant.
When attempting to provide emulsion or suspension formulations, difficulties are encountered with respect to providing a high concentration of the agriculturally active ingredient, as when such agriculturally active chemicals are formulated into an emulsion, it is difficult to maintain the emulsive state. This make it difficult to maintain a uniform formulation, particular when the formulation is diluted with water for application which may result in uneven application and thus, haphazard results.
The agriculturally active ingredient is typically mixed with one or more of a variety of conventional solvents and an emulsifying agent to form a concentrate which may be an emulsion, a suspension or a solution. The concentrate is then stored until transported to the site of use or may simply be transported and stored at the site of use. In any event, the concentrate normally will undergo some period of storage until it is ready for use. Understandably, it is most desirable to be able to transport the agriculturally active ingredient at the highest concentration possible so as to minimize the volume of material needed for transport. However, at the use site, it is normally not feasible to admix ingredients together or to process them other than to dilute the concentrate with water. Accordingly, it is important that the concentrate emulsify easily, i.e., exhibit good "bloom", upon the addition of water Once made, it is often necessary to store the diluted concentrate for extended periods of time until application. Thus, it is important that the diluted form of the concentrate exhibit good stability with respect to the uniformity of the emulsion and to avoid precipitation of the active ingredients. If non-uniformity or precipitation occurs in the diluted form, this non-uniformity will result in the non-uniform application of alternately high and low concentration formulation.
It is also desirable to increase the efficacy of a given agricultural compound relative to its loading content. It has been theorized that microemulsions can improve the efficacy of agriculturally active compounds relative to equivalent levels of the same compounds in a macro emulsion composition. See Skelton, P. R., Munk B. H., and Collins, H. M., "Formulation of Pesticide Microemulsions" Pesticide Formulations and Application Systems: 8th Volume ASTM STP 980, D. A. Hovde and G. B. Beestman, Eds, American Society for Testing and Materials, Philadelphia, 1988. Microemulsion means an oil in water or water in oil, transparent thermodynamically stable dispersion of two or more immiscible liquids wherein the dispersed phase consists of small droplets with diameters in the range of about 10 to 100 millimicrons. Such microemulsions are clear and contain at least 80% by weight water. Clear or transparent as applied to a microemulsion means that the composition appears as a single phase without any particulate or colloidal material or a second phase being present when viewed by the naked eye.
Most of the agricultural chemicals are substantially insoluble or insoluble which means that for all practical purposes, the solubility of the compound in water is insufficient to make the compound practically usable in an agricultural end use without some modification either to increase the solubility or dispersability in water, so as to increase the compound's bio-availability or avoid the use of excessively large volumes of solvent.
Agriculturally active chemicals or ingredients means compounds or mixtures thereof which can be used as agricultural fertilizers, nutrients, plant growth accelerants, herbicides, plant growth controlling chemicals and chemicals which are effective in killing plants, insects, micro-organisms, fungi, bacteria and the like which are commonly referred to as insecticides, bactericides, fungicides, nematocides, fumigants, synergists, i.e., compounds which when used in conjunction with other agriculturally active chemicals enhance their activities and the like as well as any other chemicals having properties which are suitable for agricultural uses in terms of application to plants or domestic uses for controlling insects and pests.
To produce emulsifiable concentrates and micro emulsions, it has been proposed to use C.sub.1 -C.sub.4 lower alkyl pyrrolidones such as described in South African Patent Application No. 695,393 filed Jul. 25, 1969. Additional compounds which provide emulsion stability on dilution are described in U.S. Pat. Nos 5,071,463 and 5,156,666 assigned to the ISP Investments, Inc., the common assignee herewith. While such compounds may be acceptable for producing compositions which deliver effective amounts of an insoluble agriculturally active compound with improved. stability with respect to the emulsion, the search continues for other compounds which may be usable for producing stable emulsifiable concentrates and/or microemulsions of such substantially insoluble compositions.